New observations of the space rock in the sights of NASA’s 2016 OSIRIS-REx mission --- due to take an actual physical sample of the asteroid 1999 RQ36 and return it safely to a Utah desert by 2023 --- signal that it’s an ideal target from which to secure some of the solar system’s most primitive matter.

A German-led team armed with new space- and ground-based observations of this pristine near-earth asteroid, reveal that it's likely to be an extremely porous rubble pile that should harbor secrets from the earliest stages of our solar system’s formation some 4.56 billion years ago.

The OSIRIS-REx mission represents NASA’s first attempt at such an asteroid sample return mission.

Thomas Mueller, an astronomer at Germany’s Max Planck Institute for Extraterrestrial Physics (MPE) in Garching and the lead author of a forthcoming journal paper detailing the observations, says that, previously, the asteroid’s key properties were “poorly known.”

But Mueller and colleagues’ observations with the Herschel Space Observatory, coupled with data from two other telescopes, enabled his team to garner new details about its structure and potential makeup. The team was able to confirm that the slightly-elongated 1999 RQ36 ranges some 480 to 511 meters in diameter, or at least a hundred meters smaller than previously thought. Its smaller diameter is also good news, since there is still one chance in 1800 that the object could slam into earth in 2182.

Mueller says both his own team’s observations of 1999 RQ36 with the Herschel Space Observatory and the upcoming OSIRIS-REx mission offer a significant contribution to the characterization of such near-earth objects in general.

“Accurate descriptions of these bodies are essential to understanding their formation and evolutionary processes,” said Mueller, whose research was conducted independently of the OSIRIS-REx team.

Mueller says because such asteroids' thermal properties also play an important role in making future orbit predictions, his team is, thus, also contributing to a better understanding of this Potentially Hazardous Asteroid’s (PHA) orbital mechanics.

Dante Lauretta, the OSIRIS-REx mission’s Principal Investigator and a planetary scientist at the University of Arizona, reports Mueller’s findings have already been incorporated into his team’s mission planning. The mission, scheduled to arrive at the asteroid in October of 2018, will globally map 1999 RQ36’s chemistry and mineralogy before taking its highly-prized samples in July of 2019.

“The [Mueller] findings confirm that 1999 RQ36 has properties that are favorable for the sampling of granular regolith and for the science goal of returning primitive material,” said Patrick Michel, a planetary scientist at France’s Observatoire de la Cote d’Azur and OSIRIS-REx team member. “1999 RQ36’s bulk density is about the same as water, so the asteroid must be very porous. This porosity could be in the form of micro porosity (think pumice) or macro porosity (think large voids and a rubble pile structure) or probably even both.”

Now only visible with the largest ground-based telescopes or from space, 1999 RQ36 currently lies about one earth-sun distance away.